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Journal of Mechanical Science and Technology, Vol. 19, No. 1, pp. 97-105, 2005 97 A Scheme for an Internet-based Checking Method of Machine-Tools with Variant CNC Architecture Dong-ttoon Kim* Department of Intelligence and Precision Machines, Korea Institute of Machinery and Materials, Daejeon 305-343, Korea Sun-Ho Kim Mechatronics Engineering Major, College of Engineering, Dong-Eui University, Busan 614-714, Korea Kwang-Sik Koh School of Electrical Engineering and Computer Science, Kyungpook National University, Daegu 702-701, Korea This paper proposes an Internet-based checking technique for machine-tools with variant Computerized Numerical Controller (CNC). According to its architecture, CNC is classified into one of two types : Closed Architecture Controller (CAC), which is the conventional CNC, or Open Architecture Controller (OAC), which is a recently introduced PC-based controller. Since CAC has a closed architecture, it is dependent on CNC vender specification. Because of this, it has been very difficult for users to implement application programs in the CNC domain. Recently, the conventional CNC of machine-tools has been replaced by a PC-based open architecture CNC. However, now many conventional CAC machines are being operated together with OAC machines in inadequately equipped shop floors. For Internet-based checking for variant CNC machines with CAC and OAC, a suitable systematic environment is necessary. Through this research, for the global management of variant CNC machines both a CAC and an OAC in the manufacturing system, a suitable environment for Internet-based checking of variant CNC machines was designed, and the checking methods for CAC and OAC machines were compared. The results of this research may serve as a base model for global monitoring and remote control in an integrated manufacturing system with variant CNC machines. Checking points defined in this research are classified into two categories: structured point and opera- tional point. The former includes the vibration of bearing, temperature of spindle unit, and other points of periodical management, while the latter includes oil checking, clamp locking/ unlocking, and machining on/off status. Key Words : Internet-Based Checking Method, Variant CNC, CAC, 0AC I. Introduction Widespread use of computers and the Internet * Corresponding Author, E-mail : kdh680 kimm.re.kr TEL : -t-82-42-868-7148; FAX : -t-82-42-868-7150 9 Department of Intelligence and Precision Machines, Korea Institute of Machinery and Materials, Daejeon 305-343, Korea 9 (Manuscript Received June 11, 2004; Revised October 25, 2004) have led to a continuously increasing demand for Internet-based control and monitoring of CNC machines for distributed global management in manufacturing systems. In the past, the contact points of Programmable Logic Controller (PLC) were utilized for the monitoring of I/O signals associated with CNC machines and peripheral equipment in manufacturing systems. However, this solution has been limited to the monitoring of CNC internal information. It has Copyright (C) 2005 NuriMedia Co., Ltd. 98 Dong-Hoon Kim, Sun-Ho Kim and Kwang-Sik Koh been difficult to check various monitoring data regarding the CNC, peripheral equipment, and other external units by implementing user-defin- ed programs to the CNC domain (Rober and Shin, 1995 ; Lee et. al., 2004). The required user- defined programs are application modules for the monitoring of CNC machines and for com- munication with a remote site. Recently, a conve- nient environment able to implement user-defin- ed programs to a CNC domain for remote moni- toring and control has been provided, since the conventional CNC of machine-tools has been replaced by a PC-based open architecture CNC (Rober and Shin, 1995 ; Kwon et. al., 2000 ; Hong et. al., 2003). However, many conventional CAC machines are now being operated in inadequately equipped shop floors. In order to do a remote check on such variant CNC machines, a suitable environment for each case of the CAC and the OAC should be constructed. We will now briefly outline the related re- search. Regarding research on the management of machine-tools with open architecture CNC in manufacturing systems, there have been studies on rapid part realization in flexible factory sys- tems (Wright, 1995) and on automatic configura- tion and dynamic reconfiguration (Oldknow and Yellowley, 2001). A study on switching function generators addressed the maintenance mechanism of machine-tools with open architecture CNC (Kim et al., 2002). Remote control and monitoring of machine tools by client-server environments has also been investigated (Oldknow and Yellowley, 2001; Kim et al., 2003). The representative examples for such remote services are factory windows and remote systems that are developed by a com- mercial CNC vendor (Kim et al., 2000 ; Kang and Kang, 1999). However, these systems are char- acterized by basic technical support in local domain environments. Besides of this, as for re- search on Internet-based management of mac- hine-tools, CNC-implemented fault diagnosis and basic remote services were reported (Kim et al., 2003). Web-based monitoring has been stu- died in a flexible manufacturing system (Jung et al., 2001). Furthermore, Public Switched Tele- Copyright (C) 2005 NuriMedia Co., Ltd. phone Network (PSTN) and digital I/O modules were utilized for research on the maintenance of CNC machines (Hyun et al., 1998). However, these researches have focused on only OAC machines except CAC machines and the most service function is to transmit moni- toring data via telephone line or external net- work such as Internet. Although in the case of Internet-based application, a special client-ter- minal program, which is dependent of developer, has to be installed because the most cases are based on client-server configuration. In some special cases, an additional kernel is optionally required. Besides, the third-party of superior CNC vendor such as Siemens supports partially the web services via Internet. However, in this case, the service functions are not often suitable to the shop-floor and the modification of the functions is very difficult. In domestic case, even representative CNC vendor can not service gen- erally and commercially the Internet-based chec- king services such as conditions monitoring via lnternet. The cause of such actual circumstance mentioned above is because most operators and CNC vendors have focused on the stability and original ability of CNC in domestic CNC market. That is, most CNC vendors are afraid of the breakdown of CNC machine-tools due to over- load and faults resulting from additional soft- ware installation or upgrade for the purpose of supporting the functions such as remote services. In short, although there are some researches av- ailable for machines with OAC, satisfied applica- tion cases are rare yet and the studies on machines with CAC have been very deficient. Especially, research on Internet-based checking for variant CNC machines with a CAC and an OAC has not been sufficiently reported due to the inconvenient development environment and inferior software- portability. This paper investigates methods for applying Internet-based checking techniques to variant CNC machines with OAC and CAC, and the two types of CNC are compared. And an efficient scheme for Internet-based checking for variant CNC machines is suggested through this study. First, remote checking and control of the digital A Scheme for an lnternet-based Checking Method of Machine-Tools with Variant CNC Architecture 99 signals associated with CAC machines and com- ponent parts by using a web I/O embedded mo- dule are introduced. Second, this paper consi- ders the remote checking of analog and digital signals associated with OAC machines by imple- menting user-defined application programs able to interface with an external server to the CNC domain, and by using a Data Acquisition Unit (DAU) able to acquire data connected with the contact points of machines and peripheral equi- pments. CAC has a closed architecture which is depen- dent on CNC vender specification. Because of this, it has been very difficult for users to imple- ment an application program in CNC. Therefore, a special, additional module is required for Internet-based application (Sena Technologies, 2002). For this, a web I/O embedded module was applied for Internet-based checking in this re- search. The module is directly attached to the TCP/IP network for communication with a re- mote site. In order to obtain the monitoring data of CNC machines, the I/O signals of the module were assigned to PLC I/O signals within CNC. On the other hand, OAC has a PC-based open architecture that operates independent of CNC vendor specification and no additional module is necessary for connection with a remote site. Because of this, a simple DAU, which is not directly attached to OAC main-board and not directly affects to CNC stability, is used for signal sensing and data acquisition via RS232/422 line without additional communication device mo- dule. For Internet-based remote checking of ma- chine-tools with OAC, a user-defined daemon for communication and application programs for web services were implemented in the form of internal function within OAC and an external server. Internet communication is performed be- tween the daemon program of the CNC domain and web script programs of the external server. 2. Structure of Variant CNC Machines and Remote Checking Directions As mentioned above, the implementation of a Copyright (C) 2005 NuriMedia Co., Ltd. user-defined application program is much more difficult in the CAC than in the OAC due to the inconvenient development environment of the CAC. Because the CAC is fully dependent on the CNC vendor, as shown in Fig. 1 (a), the CAC cannot support the application of user-functions that can connect with the network and remotely check CNC machines in the CNC domain. How- ever, as shown in Fig. 1 (b), it is convenient for users to implement the application programs for remote checking in the OAC domain because the OAC has an open architecture based on a PC. For Internet-based remote checking of these two CNC machines that are operated together in a manufacturing system, a suitable system environ- ment must be constructed according to the struc- ture characters of the variant CNC. The conven- tional CAC with closed architecture can effi- ciently use the network-supported unit with em- bedded web server functions because connecting the I/O signals of the applied unit with the I/O signals of CNC machines is possible. This method has an relatively simple system architecture for users, but its fatal flaw is that it cannot manage multiple CNC machines simultaneously with a single server and web script program ; this meth- od, using web-server functions embedded in the device, requires that an individual Internet Pro- tocol (IP) address be associated with each ma- chine. For the recently popularized OAC with a (a) CNC with closed architecture controller (b) CNC with open architecture controller Fig. 1 Structure of variant CNC machines 100 Dong-Hoon Kim, Sun-Ho Kim and Kwang-Sik Koh PC-based open architecture environment, instead of using network-supported units that require additional unique IP addresses, a suitable method is as follows. First, a DAU is utilized in order to acquire I/O data. Then the application program for data acquisition is implemented in order to check I/O contact signals through the DAU, and the interface daemon program, that can transmit the acquired data from a CNC domain to an external server, is implemented in the CNC do- main. A particularly outstanding merit of this system is that a lot of CNC machines can be monitored and managed simultaneously without an additional device with embedded web-server functions. This method also has good expansi- bility. 3. Definition of Checking Points As shown in Table 1, the checking points defined in this research are classified into two categories : structured point and operational point. The former includes the vibration of bear- ing, and the temperature of the spindle unit and other specific units, while the latter includes oil checking, clamp locking/unlocking, and other digital checking points associated with machine operations. Table 1 Definition of checking point Structured Conditions Operational Conditions Vibration of bearings Machining On Temperature of spindle Machining Off Vibration of bearing2 Fault (No Ready) Temperature of spindle2 Oil checking Vibration of bearing3 Clamp lock/unlock Temperature of spindle3 Sub unit on/off 4. Internet-Based Checking Method for CAC Machines This section describes the application of an Internet-based checking method for CAC mac- Fig. 2 hines. In remote monitoring of checked results Copyright (C) 2005 NuriMedia Co., Ltd. and related information with CAC machines, the application program implementation and the program running environment in the CNC do- main are more limited than in an OAC environ- ment that can easily implement software func- tions. Because an additional device module is necessary, we utilized the I/O module with em- bedded minimum operating system and web ser- ver functions, as shown in Fig. 2. By applying this module, the control and monitoring of CNC machines were remotely performed in the experi- ment. The applied device module supports a total of 32 I/O contact points in order to interface with external devices. The contact points were connected with the PLC I/O signals of the CAC machine. Through these points, the machine sta- tus such as cycle start, stop, emergency stop, and machining on/off status can actually be moni- tored in a web environment. The procedure for the application test is as follows. The icons associated with the I/O device module are first designed in default html source by using the supplied device utility, and then the icons properties are assigned to specific I/O addresses. Next, network-supported java class is inserted in default html source and the source codes are compiled by the utility compiler. After that, coded web script files are transferred to the specific file index format so that they can be interpreted by the device module engine (Sena CAC Machine .q D PLC/PMC Z 176 I,. N ooo ooo _ Digital tlO Connection (Digital I/0 Interface Method) .: l Browser Ethernet cable I Hub/SwitCh t Internet-based checking configuration using embedded web I/O device for CAC machine A Scheme for an Internet-based Checking Method of Machine-Tools with Variant CNC Architecture 101 Technologies, 2002). The transferred file, that is in the form of a specific format, is a single image file format that is downloaded to flash memory, as shown in Fig. 3. In order to assign the phy- sical I/O device addresses in application source codes, the real I/O addresses are mapped with the icon properties in web script sources such as html, vbscript, and javascript, as shown in Fig. 4. Fig. 5 shows that the status of the CAC ma- chine is now checked as machining-on when the cycle-start button is selected through a web browser. And through additional analog checking experiment for structured conditions, bearing vi- bration and spindle temperature were monitored in real time. The remote checking model of the CAC machine and its implementation method are relatively simple and convenient, but a database and large-scale script files cannot be loaded. In I User-defined application modules I Cnneetor to Interact Power Supply 16po Sensor nput Conttc Point Fig. 3 Interface between embedded web I/O device and application program detail, a maximum 512 Kbytes application script program can be downloaded to the web I/O embedded device module. However, this method can be very efficient in applications as it uses an I/O board independent of other systems. Here, for remote checking, web script was coded by using java applet and was downloaded to the web I/O embedded device module. For interfacing with the I/O of the CNC machine, I/O contact points were directly connected with each other between the embedded web I/O device and the machine I/ O signals. Test results confirmed that the applica- tion system environment can be easily designed by using this checking method. Table 2 Hardware specification of used web I/O device Item Content CPU 8-bit Microprocessor 512 KB Flesh Memory Memory (User Web File/Parameter App.) Network 10-base T Ethernet (IEEE802.3) Connection External 16 point Digital Input, Connection 16 point Digital Output Internet Protocol HTTP/TCP/UDP/IP/Ethernet Board (Vendor) Dependency, Utility software IP Setting/Web Page Uploading Icons and html implementation by using device utility .1 Icons Property Setting for I/O Address Connection Building Source to Device I Dependent Format I ; Downloading File to Flash Memory I of Embedded Device Server 1 IP Connection of Device and Web . t/O Testing Fig. 4 Address setting and testing of web I/O device Copyright (C) 2005 NuriMedia Co., Ltd. Xltad,i, 808 : ,p Q Fig. 5 Checking for CAC machine by using em- bedded device server 102 Dong-Hoon Kim, Sun-Ho Kim and Kwang-Sik Koh 5. Internet-Based Checking Method for OAC Machines In the case of the OAC, an additional device module for network support is not required, as the OAC has a convenient structure that can implement network application programs. To check and acquire machine I/O signal data, only a signal processing board or external DAU for data acquisition is needed. As most OAC is based on a single board computer with a compact ar- chitecture, a DAU that can simply Connect I/O signals is more efficient than the board type (Advantech, 2002). The application of a checking method that can notify the checking time and the replacement time of component parts was tried by monitoring of machining status, temperature, and vibrat